System and method for detecting short circuit sensor lines Okeru fire monitoring system using multiplex transmission

摘要

PURPOSE:To protect and detect the short circuit of a sensor circuit by dropping forcibly the voltage level of the sensor circuit down to a prescribed level when the circuit level drops less than the report transmission level of a sensor at the repeater side and at the same time transmitting a short circuit detecting signal to a fire receiver. CONSTITUTION:A fire receiver 1 is connected the repeaters 2 via a multiplex signal line l1 and a sensor power circuit l2 respectively. Each repeater 2 monitors the voltage level of a sensor circuit l3 and outputs a short circuit detecting signal via a short circuit detecting signal when the monitors voltage drops less than the levels produced at transmission of reports of the sensors S and SA. A short circuit holding circuit is added to drop the voltage of the circuit l3 down to a fixed safe level at reception of the short circuit detecting signal. Then a short circuit alarm signal is outputted for the circuit l3 when the receiver 1 receives continuously the short circuit detecting signals from the repeater 2 in the prescribed frequency set previously. Thus it is possible to protect and detect the short circuit of the circuit l3.